In 2009, Cowan joined the Tasmanian Tigers where a successful season saw him score 225 vs South Australia in his first game at home. This was followed on by two other centuries at Bellerive Oval and a successful Ford Ranger Cup premiership. In 2011 Cowan published a book, his diary of the 2010/2011 Sheffield Shield season entitled In the Firing Line. Cowan was selected for Australia A in June 2010 to play Sri Lanka, where he scored a century in a convincing series win.

Cowan made his Test cricket debut for Australia in the 2011 Boxing Day Test against India. His selection followed a season in which, to that point, he had averaged 64.22 in first class matches.[3] Against India he became the 18th Australian opening batsman to score a half-century (68) on debut.[4] He played in all four Tests of the series, opening the batting with David Warner. Australia won the series 4–0; over the four Tests Cowan scored 206 runs at an average of 34.33,[5] including another half-century (74) in Perth.[6] Cowan had less fortune in the Tour of the West Indies later that year, scoring only a half century. As a result, his position as opener will rely on his performances against the touring South Africans in November in which he scored over a century with his partnership with Michael Clarke.

His maiden Test century came on 12 November 2012, a year to the day after the death of his mentor and former teacher Peter Roebuck; Cowan dedicated the century to Roebuck's memory.[7] Cowan was criticized after being unable to follow up with another century in the remaining tests against South Africa. Cowan finished the series with 228 runs in five innings, these included the debut test ton and a half century in the last match at the WACA.

Cowan had a bad start to the series against Sri Lanka making 4 on his home turf in the first innings. Cowan made sure he did not have another failure in the second innings by posting 56 in an opening stand worth 132 with partner David Warner.[8]

Cowan scored 86 runs off 238 deliveries in Mohali during the Australian's tour of India. During this innings, Cowan and fellow opener David Warner achieved the highest opening partnership for Australia in India, with 139 runs. In the fourth Test, Cowan scored 38 before being bowled by Ravichandran Ashwin

Cowan is married to Australian television and radio presenter Virginia Lette.[9] Virginia gave birth to their first child, a daughter, Romy, in August 2012.[10]

According to the Sydney Morning Herald, Cowan "has a commerce degree, written a warts-and-all diary about life as a cricketer, grows his own vegetables, immerses himself in novels, and appreciates modern art and loves music."

When he was called from the SCG Members bar in 2005 to field as the 13th man for Australia against Pakistan for five minutes, he refused to keep the gear he was offered because Cowan did not believe he deserved it. Then, when NSW prematurely presented him with his baggy blue after he was picked as 12th man for the state's one-day team, he marched into Cricket NSW boss Dave Gilbert's office and handed it back, saying he would accept it when he was entitled to wear the cap.[11]

He has faced difficulties by stating in an interview with The Australian, "Perception is often reality when it comes to selection," Cowan wrote. "Throughout my career, even as a junior, I have battled against a perception that a kid who went to a good school (in his case Cranbrook) and had a degree must be soft as butter."